1. Field of the Invention
The present invention generally relates to a technique for backing up and restoring data. More particularly, the present invention pertains to design and implementation of a method and apparatus for mapping virtual drives.
2. Description of the Related Art
Today's information technology (IT) administrators are faced with the daunting task of ensuring business continuity by protecting their company's data. This is owing to the fact that backup operations are becoming increasingly complex due to mixed environments, as well as the need for increased application availability that requires those applications to be backed up even while in use. Particularly, three key challenges facing IT administrators during backup operations are: incomplete backups, minimal or no backup window and application performance and availability during backup.
Traditional backup processing degrades the performance of other applications running on the server, and frequently requires a dedicated window of time when the system is unavailable to end-users.
Off-host backup is a backup operation that takes place on a host other than on the system hosting an application that reads or writes the data being backed up. For instance, VMWARE VIRTUAL MACHINE FILE SYSTEM (VMFS) allows a proxy server to backup a snapshot of a virtual machine while the virtual machine is simultaneously reading and writing to its storage.
Some of the key benefits of off-host backups include: backup load moved from the protected resource to the backup server, backup window effectively eliminated, data integrity of applications ensured prior to backup and minimum impact on the application server when performing off-host backups. However, in certain applications off-host backup too suffers from numerous problems.
In certain applications, there is a need to backup a virtual computer (GUEST OS) comprising a virtual drive array to a storage area network (SAN) or any other form of back-up device. For example, applications that demand performance of off-host backup of a VMWARE ESX GUEST OS onto SAN. Operationally, a copy of the GUEST OS (virtual computer/machine) is copied to the SAN. A backup proxy then backs up the GUEST OS which is a collection of files that make up the virtual drives, but can not access individual files of that GUEST OS. Since the data within the virtual drive is “virtualized”, a physical mapping of where the data is stored is not available. As such, the backup software will create an image of all the files (or a selected volume of files) in the virtual drive and store them as a backup on the SAN. Consequently, upon restoration the entire image is restored from the SAN. If restoration of a single file is required, the image must be mounted, the file extracted and restored, then the image is dismounted. If the image is stored on tape, the process is very slow as the entire image is mounted from tape to facilitate restoring a single file.
Therefore, there is a need in the art for a method and apparatus for mapping virtual drives to facilitate individual file access from a virtual machine for such purposes as file restoration without mounting an entire image.